In digital mobile telephone systems, such as in the GSM system, it is possible to send short text messages: so-called short messages. In the GSM system, this is known by the name of Short Message Service (SMS). Thus, in addition to calls and data transfer, the GSM system provides in the form of a short message service a two-way paging system-like service.
The advantage of short messages compared to calls is that they can be delivered to a receiver although the receiver could not be contacted precisely at the time of transmission. This is implemented by dividing the transmission of a short message from one mobile station to another into two parts. First, from a transmitting mobile station (or e.g. a computer) to a Short Message Service Centre (SM-SC), where the short message is stored and transmitted further to the actual destiny, i.e. to a receiving mobile station when it can be contacted. Short message communication is not connection oriented but connectionless communication, i.e. there, no connection is first established between a transmitting device and a receiving device but, in a short message service, messages are transferred by pushing the messages stored in a specific short message service centre, addressed to a wireless terminal, to the receiving terminal as soon as the wireless terminal can be reached. Thus, it can be said that the short message service centre delivers a short message to a mobile station using a connectionless push method.
Short message communications have proved extremely popular and in Finland, even as much as 10% of the turnover of one operator comes from short messages. Due to the popularity of short message communications, other corresponding communication services, wherein a message is transferred almost in real time to a receiver have been started to be developed. One such new form of communication is picture messaging in the Nokia 3210 phone, where a picture is, however, transferred in a short message. Picture messaging enables the transmitting of a graphic picture message of the size of 72*28 pixels from a computer or a mobile station to another mobile station. Furthermore, in a picture message, there can further be 120 ASCII characters of text at a maximum. In addition, with a Nokia 9110 Communicator, it is possible to transmit and receive an electronic business card containing a JPEG picture. The transmission is effected as a plurality of concatenated short messages.
Further, a multimedia messaging service is being developed for a wireless mobile network, where it would be possible to transmit messages containing multimedia components, i.e. besides pictures and text that are in an electronic format (e.g. in JPEG and GIF format) also short video clips (e.g. in MPEG format) and audio clips (e.g. in MP3 format). In addition, a multimedia messaging service would enable/is expected to enable the transmitting and receiving of files that require a wider bandwidth, such as big image or data files. The intention is also to implement the multimedia messaging service in a manner similar to the short message service by using the push principle, where a message is delivered to a receiving device as soon as it can be reached. For example, WAP communication (Wireless Application Protocol) can be used as a bearer or, in future systems, a mobile communication system of the third generation.
These types of communication services that act on the push principle have specific problems. Namely, e.g. the transmission of a short message is effected as follows:                1) A sender writes with his terminal a message, e.g. “Hi, John. Let's meet in the café that is the first one from the railway station towards the ski resort. It is at the corner. Tom”        2) The sender selects the telephone number of a receiver and sends the message.        3) Within a few seconds, the terminal of the receiver typically informs of the arrived message, e.g. by peeping, and the message “Text Message Arrived” appears on the display of the terminal.        4) The receiver presses the “Read” key, whereupon the message in question will be displayed on the display of the receiving terminal.        
Because messages are delivered according to the push principle, they come directly to a receiver without the receiver being asked, and they will be displayed on the display of the receiver's device as soon as the “Read” key is pressed. This has resulted in that also undesirable messages come to the receiver, e.g. advertisements and other non-subscribed information, as well as e.g. messages of adult services. In multimedia communication, the receiving of undesirable messages may be more offensive than undesirable short messages due to multimedia components being included in the message, such as still pictures, video an audio clips. Therefore, in some countries, it is forbidden to advertise services with the help of short messages. On the other hand, if the content of short messages could be controlled advertising would indeed benefit consumers. A consumer could, for example, get calls or the right of use of some messaging service free of charge provided that he also agrees to receive advertisements.
Similar problems may just as well be encountered in the receiving of messages or other electronic information arriving according to the pull principle. A terminal may, effected by a user, for example, download a file from some server (e.g. a web server or WAP server) without exactly knowing what the file contains. In this case, the user downloads the electronic information consciously, but may nevertheless get undesirable information.
Furthermore, multimedia messages in particular are large in size, whereupon delivering them to a terminal is slow and consumes a lot of airtime. In addition, the receiving of a multimedia message requires a lot of processing of the receiving terminal, whereupon receiving consumes a lot of current. Wireless terminals normally operate by a chargeable battery and the current consumption is minimized as far as possible, because the operating time of a battery is an important criterion for the user of a terminal. Hence, the receiving of unnecessary, undesirable messages also results in additional current consumption, which will more quickly lead to the running down of the battery. The battery's operating time is particularly critical in small-sized hand-held terminals, such as mobile phones, which by reason of their size and weight have a small battery. Also for this reason, it would be good that the receiving of undesirable messages, particularly for wireless battery-operated terminals, could be prevented or at least controlled.